CN103858027B - Color filter and display device having same - Google Patents

Abstract

Provided are a color filter for use in a three-color display device capable of displaying bright colors and beautiful white and black, and a display device including the color filter. The color filter is used in a display element, which is composed of the color filter combined with a display layer that displays white and black. The display element includes a colored pixel consisting of a first sub-pixel representing a first color and a second sub-pixel representing a second color, the second color being the complement of the first color.

Description

Color filter and display device having same

technical field

The present invention relates to a color filter and a display device provided with the same, and particularly relates to a color filter for an electrophoretic display device and an electrophoretic display device provided with the color filter for an electrophoretic display device.

Background technique

In recent years, a liquid crystal display panel using a backlight has become mainstream as an image display panel, but it places a heavy burden on the eyes and is not suitable for continuous viewing for a long time.

A reflective display panel including an electrophoretic display layer between a pair of electrodes has been proposed as a display device that places less burden on the eyes. The electrophoretic display panel displays characters and images by reflecting light similarly to the printed paper surface. Therefore, the burden on the eyes is small, and it is suitable for continuous viewing of the screen for a long time.

At present, in terms of the structure of the electrophoretic display panel, the two-color display mainly black and white display is the mainstream, and it is proposed to set a color filter composed of pixels of red, green and blue three primary colors on the electrophoretic display layer to perform multi-color display. Display device (for example, refer to Patent Document 1).

On the other hand, although it is a multi-color display, it is not a full-color display. As long as it can display a total of three colors other than white and black, it has sufficient uses. If the above-mentioned full-color color display device is used for such an application, the color display becomes dark and it becomes difficult to display bright white.

prior art literature

patent documents

Patent Document 1: Japanese Unexamined Patent Publication No. 2003-161964

Contents of the invention

The problem to be solved by the invention

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a color filter for a display device capable of bright color display and beautiful white and black display, and a display device including the color filter.

means of solving problems

In order to solve the above-mentioned problems, a first aspect of the present invention provides a color filter used in a display element configured by combining the color filter with a display layer displaying white and black, wherein, as a colored pixel , including only the first sub-pixel representing the first color and the second sub-pixel representing the second color, and the second color is the complementary color of the above-mentioned first color.

The color filter can also contain transparent third sub-pixels. In addition, one pixel is composed of the first sub-pixel, the second sub-pixel, and the third sub-pixel.

In this case, with respect to the area of the first sub-pixel being 1, the area of the second sub-pixel can be set to 0.5-2, and the area of the third sub-pixel can be set to 0-7.5. In addition, the first sub-pixel may be a red colored layer, the second sub-pixel may be an indigo colored layer, and the third sub-pixel may be a transparent resin layer or a void.

A second aspect of the present invention provides a display device including: a display layer displaying white and black; and the color filter described above being formed on the display layer.

This display device can be a reflective display device, and the display layer can be an electrophoretic display layer. In addition, the above-mentioned electrophoretic display layer can be a microcapsule layer in which microcapsules containing white particles and black particles are dispersed in a resin.

Invention effect

According to the present invention, there are provided a color filter used in a display device for three-color display capable of bright color display and beautiful white and black display, and a display device including the same.

Description of drawings

FIG. 1 is a cross-sectional view showing an electrophoretic display device including a color filter according to an embodiment of the present invention.

FIG. 2A is a diagram illustrating color display of an electrophoretic display panel according to an embodiment of the present invention.

FIG. 2B is a diagram for explaining color display of an electrophoretic display panel according to an embodiment of the present invention.

3A is a diagram for explaining color display of a conventional full-color electrophoretic display panel.

3B is a diagram for explaining color display of a conventional full-color electrophoretic display panel.

FIG. 4A is a diagram for explaining color display of a conventional monochrome electrophoretic display panel.

FIG. 4B is a diagram for explaining color display of a conventional monochrome electrophoretic display panel.

detailed description

Hereinafter, embodiments of the present invention will be described in detail.

In addition, regarding the number of displayable colors, the following embodiments are examples, and are not limited to the following descriptions.

FIG. 1 is a cross-sectional view showing an electrophoretic display device including a color filter according to an embodiment of the present invention.

In the electrophoretic display device shown in FIG. 1 , an electrophoretic display layer 13 is formed with an adhesive layer 12 interposed therebetween on a substrate 10 having pixel electrodes 11 having a predetermined pattern on its surface. The pixel electrodes 11 are connected to respective switching elements, and positive and negative voltages can be applied between the pixel electrodes 11 and the transparent electrode layer 14 . The electrophoretic display layer 13 is obtained by fixing microcapsules enclosing a dispersant obtained by dispersing the electrophoretic element in a dispersion liquid with a binder resin.

On the electrophoretic display layer 13, a transparent electrode layer 14, a color filter 15, and a protective film 16 are laminated in this order. The color filter 15 includes sub-pixels of two colors in a complementary color relationship, for example, a red sub-pixel R, an indigo sub-pixel C, and a transparent sub-pixel T are configured as one pixel. In this case, each sub-pixel is provided corresponding to the pattern of the pixel electrode 11 .

The electrophoretic display layer 13 is formed by fixing microcapsules obtained by dispersing two types of particles having different electrical polarities in a transparent dispersant in the microcapsule shell with a binder resin.

As two types of particles with different electrical polarities, there is, for example, a combination of black particles and white particles. For black particles, in addition to inorganic pigments such as inorganic carbon, fine powders such as glass or resin, and their composites, etc., can be used. On the other hand, as white particles, known titanium oxide, silicon dioxide, White inorganic pigments such as alumina and zinc oxide, organic compounds such as vinyl acetate emulsions, and complexes thereof.

The color filter 15 can be formed by photolithography of a colored resist film as in the color filter for a liquid crystal display device. In the case of a color filter used in an electrophoretic display device like this embodiment, Next, it can be formed by forming a receiving layer (receptive layer) and applying various inks on the receiving layer. The receiving layer is formed by applying a coating solution for forming a receiving layer containing a resin.

As the receiving layer, polyurethane resin, polyester fiber, acrylic resin, vinyl alcohol resin, etc. can be used. In addition, porous substances such as synthetic silica and alumina may be contained in the receiving layer to improve the solvent absorption of the ink. Formation of the receiving layer can be performed by screen printing, offset printing, spin coating, or mold batch coating in the case of performing sheet-by-sheet processing. In addition, in the case of continuous roll-to-roll processing, general-purpose coatings such as die coating, comma coating, curtain coating, and gravure coating can be used. Coating technology to form. In addition, the coating solution for forming a receiving layer after coating is dried. As a drying method, heating, air blowing, or the like can be used.

As a method of applying ink to the receiving layer of the color filter of the present embodiment, since a black matrix for dividing one pixel is not formed, it is necessary to distinguish the application by color, so the screen printing method, Offset printing method, inkjet printing method, etc. Among them, the inkjet printing method is preferably used to form the color filter by ejecting the ink onto the receiving layer for reasons of easy alignment and high productivity.

As the ink for forming the color filter 15, a known coloring pigment or an ink containing a coloring dye can be used. As described above, the color filter 15 includes only sub-pixels of two colors in a complementary color relationship as colored pixels. The two colors in the complementary color relationship are not limited to red and indigo, and there are combinations of magenta and green, and combinations of yellow and indigo. Any combination of colors can be used as long as they are in a complementary color relationship to become white by color mixing.

Each of the two-color sub-pixels in a complementary color relationship does not necessarily need to be composed of a single colored layer, and may be a plurality of colored layers of different colors, and the plurality of colored layers express a predetermined color by mixing colors. For example, the indigo sub-pixel C may be composed of a green colored layer and a blue colored layer that express indigo by color mixing.

In the example shown in FIG. 1 , the color filter 15 is composed of two color sub-pixels (red sub-pixel R, indigo sub-pixel C) and a transparent sub-pixel T in a complementary color relationship, but the transparent sub-pixel T may not be included. , and only consists of two-color sub-pixels in a complementary color relationship. The transparent sub-pixel T may be made of transparent resin, or may be a void.

In two-color sub-pixels in a complementary color relationship, the coloring area ratio in the sub-pixel does not have to be 100%, but needs to be 20% or more. This is because, when the colored area ratio in the above-mentioned sub-pixel is lower than 20%, no color is expressed. In addition, from the viewpoint of expressing beautiful colors, it is preferable that the colored area ratio in the sub-pixel is 30% or more. Here, the colored area ratio refers to the ratio of the area of the colored portion in the sub-pixel to the area of the sub-pixel in two color sub-pixels in a complementary color relationship.

Here, red refers to visible light having a wavelength of about 622 to 770 nm, and the complementary color refers to indigo, which is light that absorbs light in this wavelength range and transmits light of other wavelengths.

As shown in FIGS. 2A and 2B to 4A and 4B described below, the arrangement of subpixels in one pixel of the color filter can be a diagonal arrangement or a stripe arrangement. In this case, in order to prevent color mixing, it is preferable that colored sub-pixels be arranged diagonally.

The number of sub-pixels included in one pixel is not particularly limited, and the total area of sub-pixels colored in each color (hereinafter referred to as the area of sub-pixels) may be the same or different. When there are three sub-pixels of red, indigo, and transparent, the area of the indigo sub-pixel is preferably 0.5 to 2 with respect to the area of 1 of the red sub-pixel. When the area of the indigo sub-pixel relative to the area 1 of the red sub-pixel is less than 0.5, the redness tends to increase during white display, and if it exceeds 2, the brightness during white display tends to decrease. In addition, the area of the transparent sub-pixel is preferably 0-7.5, more preferably 1-2, relative to the area 1 of the red sub-pixel. If the area of the transparent sub-pixel exceeds 7.5 with respect to the area 1 of the red sub-pixel, the color tone tends to become lighter.

The size of each sub-pixel is usually 50 to 200 μm per side in the case of a rectangle.

Next, the principle of operation of the electrophoretic display device shown in FIG. 1 will be described.

When a voltage is applied to the pixel electrode 11, the electric field applied to the microcapsule moves. When the pixel electrode 11 is a positive electrode, the negatively charged particles in the microcapsule move to the pixel electrode 11 side, and the positively charged particles move to the transparent electrode layer 14 side. Similarly, when the pixel electrode 11 is a negative electrode, the positively charged particles in the microcapsule move toward the pixel electrode 11 side, and the negatively charged particles move toward the transparent electrode layer 14 side.

For example, if the black particles are positively charged and the white particles are negatively charged, and the pixel electrode 11 is set as a negative electrode, the black particles move to the pixel electrode 11 side and the white particles move to the transparent electrode layer 14 side as shown in FIG. In this case, all the light is reflected by the microcapsule layer having white particles on the surface, and passes through the color filter 15 . Since the red sub-pixel R and the indigo sub-pixel C are in a complementary color relationship, the light transmitted from them is mixed to become white light, and the light transmitted from the transparent sub-pixel T and a bright and beautiful white image are obtained.

2A and 2B are views for explaining color display of an electrophoretic display panel according to an embodiment of the present invention based on the above operation principle. The electrophoretic display panel 21 has a structure in which a color filter 23 including two colors such as a red subpixel R and an indigo subpixel C in a complementary color relationship is arranged on the electrophoretic display layer 22 for monochrome display. One pixel of the color filter 23 is composed of four sub-pixels, and the remaining two sub-pixels are composed of transparent sub-pixels T such as transparent resin.

2A shows the case where all the parts corresponding to one pixel of the electrophoretic display layer 22 are displayed in white. FIG. black, and the remaining part is displayed as white.

That is, in the case shown in FIG. 2A , all the parts corresponding to one pixel of the electrophoretic display layer 22 are displayed in white, so all the light transmitted from the color filter 23 is reflected on the electrophoretic display layer 22 and passes through the reflected light. Among the lights, the light transmitted from the red sub-pixel R and the light transmitted from the indigo sub-pixel C are mixed to display white. In the case shown in FIG. 2B , only the part corresponding to the indigo sub-pixel C of the electrophoretic display layer 22 is displayed in black, so the light transmitted from the color filter 23 passes through the electrophoretic display layer 22 corresponding to the indigo sub-pixel C. The corresponding portion is not reflected, and the portion corresponding to the remaining sub-pixels is reflected, and the light transmitted from the red sub-pixel R among the reflected light is displayed in red. If all the portions of the electrophoretic display layer 22 corresponding to one pixel are displayed in black, there will be no light transmitted through the color filter 23 to be observed, and of course a black display will be performed.

According to the structure of the electrophoretic display panel 21 shown in FIG. 2A and FIG. 2B, one color is displayed by the sub-pixels in the complementary color relationship of two colors, and the remaining sub-pixels are made of transparent resin, so bright colors (such as red ) and three colors of beautiful white and black.

FIG. 3A and FIG. 3B show a conventional full-color electrophoretic display panel 31, showing that on the electrophoretic display layer 32 for black and white display, three primary colors such as red sub-pixel R, green sub-pixel G and indigo sub-pixel B are arranged. The structure of the color filter 33. One pixel of the color filter 33 is composed of four sub-pixels, and the remaining one sub-pixel is a transparent sub-pixel T made of transparent resin or a void.

FIG. 3A shows the case where all the parts corresponding to one pixel of the electrophoretic display layer 32 are displayed in white, and FIG. 3B shows that the part corresponding to the red sub-pixel R is displayed as A case where a part corresponding to the remaining sub-pixels is displayed in black.

That is, in the case shown in FIG. 3A , all the portions corresponding to one pixel of the electrophoretic display layer 32 are displayed in white, so all the light transmitted from the color filter 33 is reflected on the electrophoretic display layer 32 and passes through the reflected light. Among the lights, the light transmitted from the red sub-pixel R, the light transmitted from the green sub-pixel G, and the light transmitted from the indigo sub-pixel B are mixed to display white. In the case shown in FIG. 3B , only the part corresponding to the red sub-pixel R of the electrophoretic display layer 32 is displayed in white, so the light transmitted from the color filter 33 is displayed on the part of the electrophoretic display layer 32 corresponding to the red sub-pixel R. Part of it is reflected and transmitted from the red sub-pixel R, and the part corresponding to the remaining sub-pixels is not reflected and red is displayed.

Comparing the electrophoretic display panel 31 shown in FIG. 3A and FIG. 3B with the electrophoretic display panel 21 shown in FIG. 2A and FIG. coloring sub-pixels, so compared with the color filter 23, the number of sub-pixels for obtaining the complementary color effect is large, and the number of white sub-pixels (transparent resin layer) is small, so the coloring image is darker and does not A bright white image can be obtained.

For comparison, FIG. 4A and FIG. 4B show an electrophoretic display panel 41 for three-color display of white, black, and one-color coloring in the same way as in the present invention. There is a configuration including a color filter 43 of one color, for example, a red sub-pixel R as a sub-pixel. One pixel of the color filter 43 is composed of four sub-pixels, and the remaining three sub-pixels are transparent sub-pixels T made of transparent resin or voids.

FIG. 4A shows the case where all the parts corresponding to one pixel of the electrophoretic display layer 42 are displayed in white, and FIG. 4B shows that the part corresponding to the red sub-pixel R of the parts corresponding to one pixel of the electrophoretic display layer 42 is displayed as In black, the part corresponding to the remaining three transparent sub-pixels T is displayed as white.

That is, in the case shown in FIG. 4A , all the parts corresponding to one pixel of the electrophoretic display layer 43 are displayed in white, so all the light transmitted from the color filter 43 is reflected on the electrophoretic display layer 42 and passes through the reflected light. Among the lights, light transmitted from the red sub-pixel R displays red. In the case shown in FIG. 4B , only the part corresponding to the red sub-pixel R of the electrophoretic display layer 42 is displayed in black, so the light transmitted from the color filter 43 is displayed on the part of the electrophoretic display layer 42 corresponding to the red sub-pixel R. A portion is not reflected, but is reflected in a portion corresponding to the remaining sub-pixels, and is directly transmitted from the transparent sub-pixel T made of a transparent resin or a void to display white.

According to the structure of the electrophoretic display panel 41 shown in FIG. 4A and FIG. 4B, in the case of displaying white in FIG. The pink color will be displayed due to the reflection on the surface of the red sub-pixel R. In addition, when displaying white, the portion of the electrophoretic display layer corresponding to the red sub-pixel R has to be displayed in black, and the red sub-pixel R is displayed as black dots, resulting in a rough display surface.

Examples and comparative examples of the present invention are shown below, and the effects of the present invention are specifically shown.

Example 1

An electrophoretic display device having the structure shown in FIG. 1 was manufactured.

Titanium oxide powder (white particles) with an average particle size of 3 μm covered with polyethylene resin and graphite black powder with an average particle size of 4 μm (black particles) surface-treated with alkyltrimethylammonium chloride were dispersed in In tetrachloroethylene, a dispersion was obtained. In this case, the white particles are negatively charged and the black particles are positively charged.

The dispersion liquid was O/W emulsified, and microcapsules were formed by a gelatin-gum complex coacervation method, and the dispersion liquid was enclosed in microcapsules. The microcapsules obtained in this manner were screened so that the particle size specification was such that the proportion of microcapsules with an average particle diameter of 60 μm and a particle diameter of 50 to 70 μm was 50% or more.

Next, an aqueous dispersion of microcapsules having a solid content of 40% by mass was prepared. This aqueous dispersion, a polyurethane-based binder with a solid content of 25% by mass (CP-7050, manufactured by Dainippon Ink Co., Ltd.), a surfactant, a thickener, and pure water were mixed to prepare a coating for forming an electrophoretic layer. liquid. This coating solution is applied to a substrate 10 made of, for example, glass, on which a pixel electrode 11 made of ITO is formed, to form an electrophoretic display layer 13 .

On this electrophoretic display layer 13, a transparent conductive layer 14 made of ITO is formed, and on top of this, a polyester resin-based receiver solution NS-141LX (Takamatsu Yushi Co., Ltd.) is continuously coated with a knife coater to form A receiving layer with an average film thickness of 10 μm was prepared.

Color filters 15 were formed on the receiving layer by color-separated printing for each sub-pixel by an inkjet method. At this time, alignment is performed, and sub-pixels are formed at positions corresponding to the pixel electrodes 11 . As shown in FIGS. 2A and 2B , in one pixel of the color filter 15 , rectangular red sub-pixels R, indigo sub-pixels C, and two transparent sub-pixels T are arranged diagonally.

Finally, the protective film 16 is formed on the color filter 15, and the electrophoretic display device is completed.

The reflectance, a*, and b* of the display surface of the electrophoretic display device manufactured as above were measured. The measurement of reflectance is carried out under the conditions of D65 light source and 2-degree parallax using a spectrocolorimeter as a measuring device. In addition, the measurement of a* and b* was carried out under the conditions of a D65 light source and a parallax of 2 degrees using a spectrocolorimeter as a measuring device.

As a result, the reflectance in white display was 30.3%, and the reflectance in red display in which only the part of the electrophoretic display layer corresponding to the indigo subpixel was black was 17.2%, both of which were high values.

In addition, in the white display, a* was -4.1, b* was -1.1, and it was a beautiful white display.

Example 2

The electrophoretic display device was completed in the same way as in Example 1 except that rectangular indigo subpixels, yellow subpixels, and two transparent subpixels were arranged diagonally in each pixel. .

In the same manner as in Example 1, the reflectance, a*, and b* of the display surface of the electrophoretic display device manufactured as above were measured.

As a result, the reflectance in white display was 30.1%, and the reflectance in blue display in which only the portion of the electrophoretic display layer corresponding to the yellow sub-pixel was black was 16.1%, both of which were high values.

In addition, in the white display, a* was -4.3, b* was -1.2, and it was a beautiful white display.

Example 3

The electrophoretic display device was completed in the same manner as in Example 1 except that rectangular green sub-pixels, magenta sub-pixels, and two transparent sub-pixels were arranged diagonally in each pixel. .

In the same manner as in Example 1, the reflectance, a*, and b* of the display surface of the electrophoretic display device manufactured as above were measured.

As a result, the reflectance in white display was 31.5%, and the reflectance in green display in which only the portion of the electrophoretic display layer corresponding to the magenta sub-pixel was black was 18.2%, both of which were high values.

In addition, in the white display, a* was -4.4, b* was -1.0, and it was a beautiful white display.

Comparative example 1

As shown in FIG. 3A and FIG. 3B, in addition to using sub-pixels for full-color display devices composed of red sub-pixel R, green sub-pixel G, indigo sub-pixel B, and transparent sub-pixel T as color filters, , an electrophoretic display device was produced in the same manner as in the examples.

For this electrophoretic display device, the reflectance, a*, and b* were measured in the same manner as in Examples. As a result, the reflectance in the white display was 15.4%, the reflectance in the red display was 4.7%, the reflectance in the blue display was 4.6%, and the reflectance in the green display was 5.8%. are relatively low values.

In addition, a* in the white display was -4.2, and b* was -1.1.

Comparative example 2

As shown in FIG. 4A and FIG. 4B, except that a sub-pixel for a monochrome display device composed of a red sub-pixel R and three transparent sub-pixels T is used as a color filter, an electrophoretic display device.

For this electrophoretic display device, the reflectance, a*, and b* were measured in the same manner as in Examples. As a result, the reflectance in white display was 25.5%, which was high, but a* was 1.5 and b* was 1.9, both of which were higher than those in Example 1, and it became reddish in white display. of white. In addition, it was observed that the portion of the electrophoretic display layer corresponding to the red sub-pixel R was displayed in black, resulting in roughness of the display surface.

As described above, the reflectance of the electrophoretic display device of Examples 1 to 3 is higher than that of the full-color electrophoretic display device of Comparative Example 1 in any case of white display, red display, blue display, and green display. High, according to the values of a* and b* in white display, compared with the monochromatic electrophoretic display device of Comparative Example 2, a beautiful white display was shown. In addition, the roughness of the display surface observed at the time of white display in the monochromatic electrophoretic display device of Comparative Example 2 was not observed in the electrophoretic display devices of Examples 1 to 3 either.

In the above, an electrophoretic display device has been described as a display device, but the present invention is not limited thereto, and can be applied to various display devices. That is, it is not limited to a reflective display device, but can also be applied to a transmissive display device. Examples of transmissive display devices include liquid crystal display devices, and examples of reflective display devices include liquid crystal display devices and electronic paper. Among electronic papers, there are electrophoretic display devices, twisting ball display devices, and powder transfer display devices. In addition, electrophoretic display devices include microcapsule-type display devices and microcup-type display devices.

Among them, when applied to a microcapsule-type display device, a bright white display can be obtained particularly, and an advantage of low power consumption can be obtained.

Symbol Description

10···substrate

11···Pixel electrode

12···Adhesive layer

13, 22, 32, 42...Electrophoretic display layer

14···Transparent electrode layer

15, 23, 33, 43···color filter

16···Protective film

21, 31, 41... Electrophoretic display panel

Claims (6)

1. A color filter, wherein: The receiving layer is superimposed on the display layer having a plurality of display areas for switching display of white or black respectively; and a colored layer coated on the above-mentioned receiving layer, 1 pixel of the above shader layer contains: 1 first coloring layer, opposite to the first display area of the above-mentioned display layer; 1 second colored layer, opposite to a second display region of the display layer different from the first display region, and in a complementary color relationship with the first colored layer; and Two transparent layers are respectively opposite to the two third display areas of the above display layer which are different from the above first display area and the above second display area, This color filter is used in a reflective display device. 2. The color filter according to claim 1, wherein, With respect to the area of the first colored layer being 1, the area of the second colored layer is 0.5 to 2, and the area of the transparent layer is 1 to 7.5. 3. The color filter according to claim 1, wherein, The first colored layer is red, the second colored layer is indigo, and the transparent layer is a transparent resin layer or a void. 4. A display device wherein, have: The display layer has a plurality of display areas for switching display of white or black respectively; The color filter according to any one of claims 1 to 3, formed on the display layer; a transparent electrode layer overlapping between the above-mentioned display layer and the above-mentioned receiving layer; and A protective film is laminated on the above-mentioned color filter, The display device is a reflective display device. 5. The display device according to claim 4, wherein, The above display layer is an electrophoretic display layer. 6. The display device according to claim 5, wherein, The electrophoretic display layer is a microcapsule layer in which microcapsules containing white particles and black particles are dispersed in a resin.